DE19952685A1 - Video signal transmission and reproduction method, involves introducing resynchronization markings into each block group before reception and reproduction of video signal - Google Patents

Abstract

The method involves a transmitter introducing several resynchronization markings into each block group before the reception and reproduction of a video signal, to prevent the propagation of an error produced in the transmission channel. The signal has a hierarchical structure with frames, block groups and macro blocks.. Resynchronization markings are inserted at predefined positions in each block group, determined to minimize the mean error propagation costs, depending on which the macro blocks between the inserted resynchronization markings are skipped. An Independent claim is also included for video signal transmission equipment.

Description

Background of the Invention 1. Field of the invention

The present invention relates to transmission and restoring a video signal, and especially on a Procedure and apparatus for transmission and re-establishment production of an error-insensitive video signal in one faulty channel.

2. Description of the Prior Art

In the case of an image bit stream using a Coders according to H. 261, H. 263 ver 1, 2 and 3 or an MPEG-4- Encoder has been encoded, variable length encoding (VLC) used to achieve a high compression rate. If in In this case, some bits in the bit stream are faulty a decoder the decoding of the bit stream after the error stick bit impossible. This is called error propagation. In in this case correct decoding is possible after a Resynchronization mark that occurs after the bit that the Has generated errors.

In the current standard procedures for reduction such error propagation become resynchronization mark such as a strip start code and a start code (GBSC) for a block group (GOB) at predetermined positions of the encoded bitstream inserted, e.g. B. at the start sections of the respective frame, at the strip start sections in the case of Using a stripe hierarchy, and at start sections a block group in case a block group is used pen hierarchy.

However, one should use a radio channel with more frequency Error generation to be transmitted bitstream more resynchronisa tion marks are inserted. If the number of to be inserted subsequent resynchronization marks should be predetermined the positions at which the resynchronization marks in the bitstream to be inserted can be determined.

In conventional technology, in order to hide the block group (GOB) in which the error occurred during the restoration of a received video signal, all macroblocks (MB) between the start code (GBSC) of the block group (GOB) in which the error occurred, and the start code (GBSC) of the subsequently decoded block group (GOB) using the motion vectors of the macro blocks (MB) of a previous block group (GOB). Fig. 1 shows the data structure of the above-mentioned error concealment. According to FIG. 1, the start code (GBSC) of the block group (GOB) is recognized in the received bit stream and decoded into the respective block groups (GOB) 100 , 102 , 104 and 106 . The decoded GOB 108 , 110 , 112 and 114 are restored at each corresponding position of a frame 116 . Here, if it is determined as a result of checking the start code (GBSC) of the third block group 104 that the second block group (GOB) 110 has an error, then the second decoded block group (GOB) 110 is discarded. Thereafter, the second block group (GOB) 110 is restored by performing motion compensation using motion vectors in the first block group (GOB) 100 .

However, since a resynchronization mark is only used as a start code (GBSC) is defined in a block group header, which is the Starting point of the block group (GOB) is in such a procedure, it should be noted that the error is at least one Block group (GOB) reproduces.

Also, a video signal is used at the receiving end Macroblocks (MB) transferred from motion vectors posed. If there is an error in the motion vectors of how of the macro blocks (MB) to be produced, the feh Learning motion vector from the motion vectors of the macro blocks (MB) derived from the previous block group (GOB). The derivation is carried out by averaging the Motion vectors of the restored macro blocks below peripheral blocks of the current macroblock. But when the current block group has been lost, it is difficult to restore the current macroblock because the derivative value of the motion vector of the current one Macroblock becomes zero.  

Even if an error occurs in a field that the Position of the macro blocks in the block group header or Strip head represents the correct position of the macro blocks from the corresponding macro because of the error block to be restored. Therefore, a procedure for the determination needs whether an error occurred in the field.

Summary of the invention

To solve the above problem, it is a goal of the present the invention, a method and an apparatus for the transfer provision of a video signal in the resynchronization markings at shorter intervals than an additional block group Lich at predetermined positions of a bit stream other than that Start parts of a frame and a block group are inserted, to prevent error propagation.

In order to achieve the first goal, a Ver drive provided for the transmission of a video signal, wherein before receiving and restoring a video signal a hierarchical structure with frames, block groups (GOB) and "'Macro blocks a transmitter a variety of resynchronization mar inserts into each group of blocks, so as to reproduce to prevent an error generated in a transmission channel change, the insertion of resynchronization marks the Steps includes: assigning the number of resynchronization marks cations for the respective block groups and insertion of the assigned ordered resynchronization marks at predetermined positions tions of the corresponding block group, the positions be determined to increase the mean error propagation costs minimize, depending on the respective between the inserted Resynchronization marks positioned macro blocks to be skipped.

To achieve the first goal, a video signal is transmitted device for inserting a variety of resynchronisa tion markings in block groups (GOB) provided to the Fort planting errors generated in the transmission channel before Receive and restore a video signal with a hierarchical structure with frame, block groups and macro  block and the apparatus contains: an encoder for encoding image data, a frame code memory cut for storing the respective encoded macroblock display values (COD) determined by the encoder a frame code storage section for storing one through bitstream generated the encoder, a resynchronization marker generator for determining the number and posi tion in the bit stream corresponding to that in the frame code Resyn to be inserted in the memory section stored COD values chronological markings and for generating the resynchroni station marks, and a resynchronization mark Joining section for inserting the generated resynchronization mark markings at corresponding positions of the saved Bit streams and for the transmission of the generated resynchronisa markings.

To achieve the second goal, a process for Restore a received video signal with a her hierarchical structure with frame, block groups (GOB) and macro block by inserting a variety of resynchronizations markings in the block groups (GOB) provided to the Fort planting an error generated in the transmission channel prevent, and the procedure includes the steps of: recognizing one Macroblock error between inserted resynchroni sations markers, removing the recovered data from a section where the fault was detected and hiding the error from the section by replacing the removed one Data section through the data of the section that immediately was previously covered.

To achieve the second goal, a video signal is reapplied Manufacturing process intended for restoring a Image from the received motion vectors of the respective Microblocks of the video signal with a hierarchical structure with frames, block groups (GOB) and macro blocks, the Motion vector of a faulty macroblock by replacing it of the motion vector by immediately before produced motion vector is derived.

To achieve the second goal, a video signal is reapplied  Manufacturing process for restoring a macro blocks provided in a position by reading a field that the position of the macroblock under the heads of the block group in a video signal with a frame, block groups and macro blocks, determining whether an error in a field, that shows the position of the macroblock was generated by Perform a parity check on the macroblock of the received video signal, which is an inserted in the field Contains parity bit, which shows the position of the macroblock.

Brief description of the drawings

The above objects and advantages of the present invention will be more apparent from the detailed description exercise of one of its preferred embodiments with reference to the attached drawings, in which:

. Figure 1 shows the data structure of a conventional incorporation means Fehlerverber shows;

Fig. 2 is a flowchart showing a video signal transmission method according to the present invention;

Fig. 3 is a block diagram showing a video signal transmission apparatus according to the present invention; and

Fig. 4 shows an example of a data structure in which a resynchronization mark of Fig. 2 is inserted.

Description of the preferred embodiments

An embodiment of the present invention will now be described in more detail with reference to the accompanying drawings. Fig. 2 is a flowchart showing a video signal transmission method according to the present invention.

All macro blocks of a kth frame are encoded (step 200 ). The coding is carried out using a variable length coding method (VLC). The bitstreams encoded with respect to all macroblocks in the kth frame are generated and stored (step 202 ). The number and positions of the resynchronization marks to be inserted at predetermined positions of the stored bit streams are determined (step 204 ). The resynchronization marks are inserted and transmitted at the determined positions of the bit stream (step 206 ). The above processes are repeated for all frames (step 208 ).

A process for determining the number and positions of the resynchronization marks to be inserted displayed in step 204 is as follows. First, the number of resynchronization marks to be inserted into the respective block groups (GOB) is determined. The number r _{j of} the resynchronization marks to be assigned to a j-th block group (GOB) is determined as shown in the following equation.

where N _j and N _{F represent} the number of macroblocks (MB) that are not skipped in the jth block group (GOB) or in a frame. R _F is the number of resynchronization marks assigned to a frame and is determined by the frequency with which a network generates errors. The expression nint (...) is an operator for rounding to the nearest whole number. For example, nint (5.2) = 5 and nint (5.6) = 6.

The number r _j of the synchronization marks assigned to the jth block group is determined by the expression r _j = max {min (r _j , N _j -1), 0}. This is because r _j should be corrected because there is at least one skipped mark between the resynchronization marks in the case of the block group (GOB) where r _j <Nj.

The positions at which the resynchronization marks associated with the jth block group (GOB) are inserted are determined as follows. If e.g. B. a bit error occurs in the kth macro block (MB) of the jth block group (GOB), due to the loss of the VLC decoding synchronization, all macroblocks from the kth macroblock to the next resynchronization marking cannot be corrected. Then correct decoding is carried out from the next resynchronization mark. Because of the above error, the error propagation cost E _j can be represented by the number of macro blocks (MB) lost in the jth block group (GOB).

c (i, j) is a binary complement of an encoded macroblock Description (COD) in an H.263 syntax. COD is 1 if the i-th MB is a non-skipped MB, and 0 if the i-th MB is a skipped MB. The value m is the number of MB in the GOB. If c (i, j) is 0, it means that the i th MB is over is jumped, and that the MB with no effect through a channel errors can be decoded by replacing with the value of the MB in the same position in a previous frame.

In order to statistically express the error propagation costs when it is assumed that the error propagation rates of the respective MB are the same, and when the error generation probability is p _e , the following average error propagation costs E _{0, j} can be determined.

According to equation (3) the error propagation costs depend each GOB by the number of MB skipped in the GOB off. If e.g. B. all MB in the GOB are skipped, then the resynchronization marks are not effective insert. If the number of MB skipped in one GOB greater than the number of MB skipped in one other GOB, then there should be more resynchronization marks assigned to the GOB, the more skipped MB so the two GOBs have essentially the same mean mistake have reproductive costs.

The case where one resynchronization mark is used in each GOB is compared to the case where two resynchronization marks are used. To simplify the explanation, it is assumed that none of the MB is skipped. If a resynchronization marker is inserted into each GOB, the mean error propagation costs are determined from equation (3) as follows:

If a resynchronization marker is inserted into the GOB after the kth MB, the error propagation costs are as follows:

According to equation (5), the mean error propagation costs fluctuate according to the position of the resynchronization marking, which is also inserted. The position k * of the resynchronization marking, which minimizes the average error propagation costs corresponding to the additionally inserted resynchronization markings, can be derived from equation (5) as follows.

Here the average error propagation costs are determined as follows.

It is noted that the mean error propagation cost according to equation (7) is reduced if another resyn chronization marker is used in the GOB. It is also noted that according to equation (6) the position of the resynchronization marker, which minimizes the mean error propagation costs, lies in the middle of the GOB.

The position k _i * of the resynchronization marker is determined as follows when a solution is found by differentiating k _i (i = 1, 2, ..., r).

According to the characteristic of the skipped MB, m is the number N _{j of} the MB that are not skipped in the jth GOB, and r is r _j .

Fig. 3 is a block diagram showing a video signal transmission apparatus according to the present invention. The video signal transmitting apparatus of FIG. 3 includes a decoder 300, a storage unit 302 for the frame COD, a Resynchroni sationsmarkierungsgenerator 304, a storage unit 306 for the frame bit stream, and a Resynchronisationsmarkierungs insertion 308th Here the encoder is an H.263 encoder.

Operation is as follows. The encoder 300 encodes a received radio signal. The storage unit 302 for the frame COD stores the encodings of the respective MB determined by the encoder 300 . The resynchronization mark generator 304 determines and generates the number and insertion positions of the resynchronization marks associated with the respective GOB after the sequence of each step of the flowchart of FIG. 2 with respect to the coding of the respective MB stored in the memory unit 302 for the frame COD the resynchronization marks.

Here, the resynchronization marks can be inserted into a data structure shown in FIG. 4. A resynchronization marker field 400 contains 17 bits, ie 16 continuous "0" and a "1". A GN field 402 contains five bits and designates the GOB numbers. A flag field 404 contains one bit and is "1". An MBA field 406 contains five bits and designates the MB numbers that are counted from the starting point of the GOB. A PQUANT field 408 contains five bits and denotes the quantization level size of a previous MB.

The frame bit stream storage unit 306 stores a bit stream generated by the encoder 300 . The resynchronization mark insertion unit 308 inserts the markings generated by the resynchronization mark generator 304 at corresponding positions of the storage unit 306 for the frame bit stream and transmits the inserted markings.

A procedure for restoring a GOB in which a Video signal with Resyn inserted into the frame bit stream transfer chronological markings as described above and received with generated errors is as follows. In the The present invention becomes a section in which an error was generated, searched by checking the MB for between the resynchronization marks inserted in the GOB. Then the data of the faulty, searched Section removed. The error is hidden by replacing it of the faulty section immediately preceding recovered and error-free section.

The received video signal is decoded and from that on carried motion vector of each macroblock poses. If an error in the motion vector of a recover macroblock to be delivered, the derivation of the Motion vector performed by replacing the motion vector tors of the current macroblock in which the error is generated by the immediately before the current macroblock restored motion vector.  

Even if an error was generated in a field, the the position of the macroblock in the GOB head or strip contains header, becomes a parity bit in the present invention inserted and transferred, which can be used to convert the Check parity in a corresponding field, so too determine whether there is an error in the field with the position of the macro blocks was created. The above parity bit is placed in the GOB or the strip head inserted and transferred, and a The recipient determines whether by performing a parity check an error in the field that shows the position of the macroblock, is present.

According to the present invention it is possible to correct the errors Prevent reproduction by inserting the resynchronisa tion marks at predetermined positions under consideration whether the macroblocks in the respective GOB have been skipped if the video signal using an error term mobile network or radio network is transmitted.

It is also possible to propagate errors in the GOB Hide macro blocks between resynchronizations prevent markings when a faulty macroblock is recognized.

It is also possible to determine whether there is an error in the field with the position of the macro block was created by inserting a parity bit into the same in the GOB header or strip header.

Claims (9)

1. A method for the transmission of a video signal, wherein before the reception and restoration of a video signal with a hierarchical structure with frames, block groups (GOB) and macro blocks, a transmitter inserts a large number of resynchronization marks in each block group (GOB), so as to continue prevent planting of an error generated in a transmission channel, the insertion of resynchronization marks including the steps:

• a) assigning the number of resynchronization marks to the respective block groups (GOB); and
• b) inserting the assigned resynchronization marks at predetermined positions of the corresponding block group, the positions being determined in order to minimize the average error of propagation costs, depending on the respective macro blocks positioned between the resynchronization marks to be inserted.

2. The method of claim 1, wherein the number of resynchronization markings of step (a) is determined by the following equation
if nint (...) an operator for rounding to integers, R _F the number of resynchronization marks assigned to the frame, N _j the number of macroblocks not skipped in a jth GOB and N _F the number of not in the frame skipped macro blocks. 3. The method of claim 2, wherein the number of associated resynchronization marks is controlled so that it is r _j = max {min (r _j , N _j -1), 0}. 4. The method of claim 1, wherein in step (b) the average error propagation cost of a jth GOB is determined by the following equation:
where r is the number of additional resynchronization marks to be inserted, k _i (i ε {1, 2, ..., r}) are the positions of the resynchronization marks to be inserted, p _{e is} a probability that an error will be generated in each macroblock and m is the number of macroblocks that are not skipped in the jth GOB. 5. The method of claim 4, wherein the position k _{i of} an i-th mark is determined by the following equation:
in order to minimize the mean error propagation costs, where r _{j is} the number of resynchronization marks assigned to the j th GOB. 6. Video signal transmission apparatus for inserting a large number of resynchronization marks in block groups (GOB) to prevent the propagation of errors generated in the transmission channel before the reception and restoration of a video signal with a hierarchical structure with frames, block groups and macro blocks, and the apparatus contains :
an encoder for encoding image data,
a frame code storage section for storing the respective encoded macroblock display values (COD) determined by the encoder,
a frame bit stream storage section for storing a bit stream generated by the encoder,
a resynchronization mark generator for determining the number and positions of the resynchronization marks to be inserted into the bit stream corresponding to the COD values stored in the frame bit stream storage section and for generating the resynchronization marks, and
a resynchronization mark insertion section for inserting the generated resynchronization marks at corresponding positions of the stored bit stream and for transmitting the generated resynchronization marks. 7. A method for restoring a received video signal with a hierarchical structure with frames, block groups (GOB) and macroblocks by inserting a plurality of resynchronization marks into the block groups (GOB) to prevent the propagation of an error generated in the transmission channel, and that The procedure includes the steps:
Detection of an error from a macroblock between inserted resynchronization marks, removal of the restored data from a section in which the error was detected, and
Hide the error from the section by replacing the removed data section with the data of the section that was covered immediately before. 8. Video signal recovery procedure for recovery len an image from the received motion vectors of the respective microblocks of the video signal with a hierarchical Structure with frames, block groups (GOB) and macro blocks, whereby the motion vector of a faulty macroblock by replacement zen of the motion vector by the immediately before posed motion vector is derived. 9. video signal restoration method for restoring a macro block in position by reading a field showing the position of the macro block under the heads of the block group in a video signal having a frame, block groups and macro blocks,
determining whether an error has been generated in a field showing the position of the macroblock by performing a parity check on the macroblock from the received video signal containing a parity bit inserted in the field showing the position of the macroblock.